Appendix A. Summary of topographic variables, derived canopy cover, and large tree density distributions.

Summary of topographic variables, derived canopy cover, and large tree density distributions

Soil carbon pools.

<p>Soil carbon pools.</p

Stand characteristics.

<p>(a) Distribution of trees (> 5 cm DBH) in 5 cm diameter classes in the prescribed fire (FIRE), control (CTRL), mechanical thinning (THN) and mechanical thinning followed by prescribed fire (THN+FIRE) treatments at Blodgett Forest (3 replicates per treatment). Tree diameter distribution was measured the year before the treatment (PRE) in 2001, the first post-treatment year in 2003 (POST_1), and seven years post-treatment in 2009 (POST_7). Each class is labeled with the lower interval limit. (b) Difference in number of trees between 2001 and 2003 (POST_1) and 2003 and 2009 (POST_7) by diameter class.</p

Tree biomass carbon stocks, growth and productivity.

<p>Tree biomass carbon stocks, growth and productivity.</p

Study layout.

<p>Map of the Blodgett Forest. The control, mechanical thinning, prescribed fire, thinning followed by prescribed fire treatments each had three replicates. Soil CO₂ flux and soil carbon pools were measured in the clear-cut harvest treatment area and one of the replicates of the control and prescribed fire treatments. Timing of treatments (treat.) and measurements (meas.) during a period of 17 years, from 1995 to 2012, is also shown.</p

Seasonal trends of soil CO2 efflux, soil temperature and soil water content.

<p>(a) Soil CO₂ efflux, (b) soil temperature (10 cm depth), and (c) soil water content (8 cm depth) recorded during 2011–2012 from profiles installed at the control (CTRL_Fs), prescribed fire (FIRE_Fs), and tree harvest with (HARV_RIP) and without soil ripping (HARV_{NO_RIP}) sites. (d) Comparisons of soil CO₂ efflux at the control site (CTRL_Fs), and soil CO₂ efflux at the fire (FIRE_Fs) and harvest (HARV) sites modeled using climate data recorded at the control site.</p

Effects of treatments on soil CO₂ efflux and soil environmental conditions.

<p>Comparison of (a) soil CO₂ efflux, (b) soil temperature, and (c) soil water content (SWC) between fire (FIRE_Fs) and harvest (HARV) treatment sites and the control site (CTRL_Fs). Each symbol represents the average of the 20–29 plots measured in 2012 using the chamber technique. The harvest data is the average of values from units with and without soil ripping. Slope and r² of the linear regression are also shown.</p

CO₂ concentration.

<p>Concentration of CO₂ measured at 2, 8, 16 and 24 cm depths at the control (CTRL_Fs), prescribed fire (FIRE_Fs), and harvest (HARV) treatment sites in 2012.</p

Soil tortuosity and diffusion.

<p>(a) Comparison of the empirically determined soil tortuosity factor at the control (CTRL_Fs), fire (FIRE_Fs), and tree harvest with (HARV_RIP) and without soil ripping (HARV_{NO_RIP}) treatment sites. Values predicted from the exponential Moldrup curve are included for comparison [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150256#pone.0150256.ref035" target="_blank">35</a>]. (b) Seasonal trend of the diffusion coefficient at the treatment sites calculated from the specific relationship between tortuosity factor and soil water content ξ = 0.007e^4.094*^(1-swc) and the CO₂ diffusivity in free air, which was affected by soil temperature, atmospheric pressure, and soil water content monitored at each site.</p

Tree growth and productivity.

<p>(a) Annual individual tree radial growth (tree ring widths, in mm yr^-1) for the control (CTRL), prescribed fire (FIRE), mechanical thinning (THN), and mechanical thinning followed by prescribed fire (THN+FIRE) treatments from 1986 to 2009 at Blodgett Forest. Samples were collected from each of the five tree species equally distributed among size classes. (b) Annual mean tree radial growth (mm yr^-1), calculated as the average tree growth of all trees in each treatment, identifies both the effect of treatments on tree increment growth (a) and the effect of treatments on tree density. (c) Stand annual productivity was expressed as the difference in stand biomass (aboveground) between two consecutive years. The rectangles show the treatment year 2002. Data are the averages from three replicates.</p